New study maps how ocean currents connect the world's fisheries

A new study published in the journal Science finds that the world's marine fisheries form a single network, with over $10 billion worth of fish each year being caught in a country other than the one in which it spawned.

While fisheries are traditionally managed at the national level, the study reveals the degree to which each country's fishing economy relies on the health of its neighbors' spawning grounds, highlighting the need for greater international cooperation.

Led by researchers at the University of California, Berkeley, the London School of Economics, and the University of Delaware, the study used a particle tracking computer simulation to map the flow of fish larvae across national boundaries. It is the first to estimate the extent of larval transport globally, putting fishery management in a new perspective by identifying hotspots of regional interdependence where cooperative management is needed most.

"Now we have a map of how the world's fisheries are interconnected, and where international cooperation is needed most urgently to conserve a natural resource that hundreds of millions of people rely on," said co-author Kimberly Oremus, assistant professor at the University of Delaware's School of Marine Science and Policy.

The vast majority of the world's wild-caught marine fish, an estimated 90%, are caught within 200 miles of shore, within national jurisdictions. Yet even these fish can be carried far from their spawning grounds by currents in their larval stage, before they're able to swim. This means that while countries have set national maritime boundaries, the ocean is made up of highly interconnected networks where most countries depend on their neighbors to properly manage their own fisheries. Understanding the nature of this network is an important step toward more effective fishery management, and is essential for countries whose economies and food security are reliant on fish born elsewhere.

The authors brought together their expertise in oceanography, fish biology, and economics to make progress on this complex problem.

"Data from a wide range of scientific fields needed to come together to make this study possible," said lead author Nandini Ramesh, a post-doctoral researcher in the Department of Earth and Planetary Science at the University of California, Berkeley. "We needed to look at patterns of fish spawning, the life cycles of different species, ocean currents, and how these vary with the seasons in order to begin to understand this system." The study combined data from satellites, ocean moorings, ecological field observations, and marine catch records, to build a computer model of how eggs and larvae of over 700 species of fish all over the world are transported by ocean currents.

The research shows that ocean regions are connected to each other in what's known as a "small world network", the same phenomenon that allows strangers to be linked by six degrees of separation. That adds a potential new risk: threats in one part of the world could result in a cascade of stresses, affecting one region after another.

"We are all dependent on the oceans," said co-author James Rising, assistant professorial research fellow at the Grantham Research Institute in the London School of Economics. "When fisheries are mismanaged or breeding grounds are not protected, it could affect food security half a world away."

A surprising finding of the study was how interconnected national fisheries are, across the globe. "This is something of a double-edged sword," explained lead author Ramesh, "On one hand, it implies that mismanagement of a fishery can have negative effects that easily propagate to other countries; on the other hand, it implies that multiple countries can benefit by targeting conservation and/or management efforts in just a few regions."

"By modeling dispersal by species, we could connect this ecosystem service to the value of catch, marine fishing jobs, food security and gross domestic product," Oremus added. "This allowed us to talk about how vulnerable a nation is to the management of fisheries in neighboring countries."

They found that the tropics are especially vulnerable to this larval movement--particularly when it comes to food security and jobs.

"Our hope is that this study will be a stepping stone for policy makers to study their own regions more closely to determine their interdependencies," said Ramesh. "This is an important first step. This is not something people have examined before at this scale."

Invitation: Global warming to cause dramatic changes in fisheriesNew research from scientists and economists at the University of California Santa Barbara, Oregon State University and Environmental Defense Fund identifies the dramatic future impacts of climate change on the world's fisheries and how fishing reforms are vital to sustaining the global seafood supply.

HKU and international researchers promote marine fisheries reform in ChinaA study highlighting the challenges and opportunities of fishery management in China has just been released in a perspective piece 'Opportunity for Marine Fisheries Reform in China' in the Proceedings of the National Academy of Sciences, USA, with the combined efforts of 18 international researchers all over the world, including an ecologist from the University of Hong Kong (HKU).

How China is poised for marine fisheries reformChina has introduced an unprecedented policy platform for stewarding its fisheries and other marine resources; in order to achieve a true paradigm shift a team of international scientists from within and outside of China recommend major institutional reform.

Profitable coral reef fisheries require light fishingFishing is fundamentally altering the food chain in coral reefs and putting dual pressures on the valuable top-level predatory fish, according to new research by the Wildlife Conservation Society, Lancaster University, and other organizations.

Best Science Podcasts 2019

AnthropomorphicDo animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.

#534 Bacteria are Coming for Your OJWhat makes breakfast, breakfast? Well, according to every movie and TV show we've ever seen, a big glass of orange juice is basically required. But our morning grapefruit might be in danger. Why? Citrus greening, a bacteria carried by a bug, has infected 90% of the citrus groves in Florida. It's coming for your OJ. We'll talk with University of Maryland plant virologist Anne Simon about ways to stop the citrus killer, and with science writer and journalist Maryn McKenna about why throwing antibiotics at the problem is probably not the solution. Related links: A Review of the Citrus Greening...